1. Field of the Invention
The present invention generally relates to an dish antenna calibration system and a method that applies the same, and more particularly, to a system inside a dish antenna for calibrating the RF pointing and a method that applies the same.
2. Description of the Related Art
The former antenna related calibration technology is the U.S. Pat. No. 5,734,356 (approved on Jun. 7, 1996), which discloses a portable disk antenna in which the mechanical structure is mainly discussed. The azimuth and elevation deviation of a disk antenna are calibrated by a compass and a level instrument respectively. However, this method can not make sure the beam aiming is precise. Additionally, the U.S. Pat. No. 5,977,906 (approved on Nov. 2, 1999) discloses an apparatus and a method for calibrating azimuth bore sight of a antenna azimuth in a radar system. The antenna is installed on a mobile vehicle and used to find a calibration target. At first, a target range and a azimuth angle are measured, then the vehicle is moved and the second target range and the azimuth angle are measured again. The inclination of both measures is used to calculate a calibration offset angle. However, this patent only discloses the method for calibrating but discloses nothing relating to its precision.
FIG. 1 is a diagram schematically showing the relationship between the elevation mechanical 0° of a conventional antenna and the pointing beam. Referring to FIG. 1, the antenna's elevation mechanical 0° 104 can be deployed to point it to the ground horizontal 0° 104, and an inclination between the antenna elevation and the horizontal line can be obtained by using the level instrument. However, for those antenna beam widths that are quite narrow, applying either method can result in an error beyond an allowable range of the system. Therefore, even if the azimuth and the antenna elevation mechanism are precisely calibrated; it is difficult to determine whether the mechanical elevation 0° and the horizontal 0° of the antenna beam are the same or not.